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In the struggle to develop better batteries, it’s the overall capacity that tends to get most of the attention — we marvel when a new smartphone crams in a few more milliamp-hours. Capacity is nothing without the longevity to survive a large number of repeated charging cycles, though. Even the most advanced lithium-ion batteries still lose capacity as they age, and there’s no way to prevent that until we know the cause, which we might thanks to two new studies from the US Department of Energy. These studies point to tiny nanoscale crystals as the culprits for reduced capacity over time.

The key to unraveling this mystery was to make careful, direct observations of the cathode and anode material used in modern batteries. Scientists had already pinpointed these components as the site of age-related battery erosion, but the specific mechanism was unclear. The team from Brookhaven National Laboratory used a very sensitive transmission electron microscope (TEM) to observe the changes in high-quality nickel-oxide anodes as they were repeatedly charged and discharged.

The experiment showed that as lithium ions pass through cathodes and anodes, they slowly become stuck within the ion channels due to reactions with nickel oxide to produce small crystals (salt buildup, essentially). These crystals alter the structure of the battery and cause other ions to move less efficiently, thus lowering the usable capacity. Surprisingly, the degradation observed by the Brookhaven team didn’t seem to follow any discernible pattern, at least at first.

The ultimate cause of a lithium-ion battery’s imperfections is that, well, its components aren’t perfect. The anode and cathode materials, no matter how carefully constructed, have minuscule imperfections that act as a nucleation site for crystal formation. It’s a bit like heating water in a totally smooth container versus one with surface disruptions. The bubbles need some sort of irregularity on which to form, and it’s the same with the nanocrystals in batteries. The team refers to this as the chink in the anode’s armor. If there is a place for the crystals to form, they will.

The second study from the Department of Energy’s National Renewable Energy Laboratory looked at the effects of charge speed and capacity on batteries, but focused more on the cathode. This research showed that the race to make higher density batteries could actually be hurting longevity — the bigger the battery and faster it charges, the fewer cycles you get before the nanocrystallization begins to affect it.

So if we can’t simply prevent these nanocrystals from forming, is there a way to reverse the process or at least slow it? It may be possible to treat battery components with a type of atomic deposition to fill in as many of the tiny gaps and imperfections as possible with nanoparticles. This would at least slow the formation of blockages in the ion channels. Even if that doesn’t solve the problem entirely, it could allow engineers to continue ramping up energy density without sacrificing durability. Careful examination of the structure of these crystals could even lead to ways of breaking them apart to revitalize old batteries.

This research might end up being more vital than efforts to boost the capacity of batteries to power faster hardware — in many cases the lifetime of a product is determined by how many cycles the battery can take. This is becoming even more important as companies increasingly push non-removable batteries in laptops, smartphones, and tablets, yet again reminding us that we truly are slaves of electricity.

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Ivor O’Connor

Water boiling and also water freezing. Have you ever seen water cooled a few degrees past 0 centigrade, freezing point, still as a liquid. Put a few impurities and instant freeze.

Anyways this whole thing sounds very similar to the process that takes place in old fashioned nickel cad batteries. The way to get over the memory issues is to overheat them so the crystals break up again. Seems like a variation on this theme could be useful here.

ranfan

Damn,you should be out there helping them out with that kind of knowledge lol

Ivor O’Connor

Naw. Just standard knowledge from having always needed batteries and being naturally curious. They have battery chargers now, which I have bought, that take in to account these memory affects. But with battery technology constantly changing as of late you must know the particular characteristics of that technology. A good article about old problems with crystals forming, I did not read the article, is probably this one http://batteryuniversity.com/learn/article/memory_myth_or_fact

James

I was thinking the same thing. I remember learning – as a tangential topic – in engineering physics (electricity and magnetism) about this build up of crystals with the nickel-cadmium batteries. It seemed logical for the same to apply to lithium-ion as well, albeit perhaps slightly different.

I also found around the same time that it’s possible to ‘restore life’ to the nickel-cadmium batteries (18V drill in my case) by hooking them up to a welder and sending a high current/voltage through them.

I have to believe the researchers on this Li-Ion project are aware of this very process for the NiCd counterpart.

EnigmaV8

Yeah I thought the same. I’ve known about crystals for years… Freeze my NiCds and then hit them firmly a few times. Works great. Not sure how this research is huge news or earth shattering.

you are welcome, and thank you for being worthless enough to comment about a comment…

EnigmaV8

…like you just did? ;)

Mirimon

exactly… or did the whole pot and kettle story never get told to you for bed time?

Harry_Wild

I glad I did not buy a hybrid car! Every 5 years or so – new battery and it not cheap! Not talking about the battery inside that use to start the car either. It the battery bank under the trunk!

Ivor O’Connor

It’s worrisome but Tesla has a great well documented 8 year warranty. Their roadsters have been in production since 2008 and have not had any problems, which they like to point out, so it is looking good. Replacement costs for their largest battery pack is only 12K. I personally think they will as time goes by start monitoring every cell in the pack and replace questionable ones free. Doing so would cost them nothing if they automate the process and avoid negative press. If they did this I would not be surprised if the battery packs became cost effective for well over 10 years.

BGood2

Where did you get this data? I sold my Camry Hybrid at 6 years and its battery was fine. A year past that and the second owner has had no problems. I can also point out Prius taxi cabs with nearly 200,000 miles on the original battery!

As for the Camry Hybrids, which debuted in 2006, I know of only one so far that has needed a new hybrid battery, and it was covered under warranty.

brunurb

I’ve had a Prius for 10 years, just reached 100K miles, and have never had a problem with the hybrid battery…

Scott

That’s because the engineers at Toyota are interested in longevity, unlike the folks that make your smartphone or laptop. Put simply, they WANT you to toast your batteries in phones and laptops so you’ll be forced to replace them… lots and lots of folks replace the entire machine, not just the batteries- You can get orders of magnitude longer life out of lith-ion by only charging to 80% capacity, and only discharging to 20%. It’s the last 20% on both ends that does the majority of the damage, and this is well known. I troubled myself to learn all of this after discovering that a battery I had literally almost never used to power a laptop at my desk was dead in two years anyway- because of windows and it’s absolute insistence on keeping the battery at >98% charged capacity. At one point I looked for a utility that would allow me to manually set the percentages that trigger “stop charging now” and “shutdown the machine now” states, but with no success. Anybody know of anything like that for a windows box? Since I never found that solution, these days, my laptop battery stays in the case, outside of the laptop, unless needed- because programmers cant fry a battery that isnt connected to a charger.

e92m3

Very interesting. This could easily be a very critical finding.
A drastic leap in overall battery efficiency (including valid production/cost/waste production concerns with our current batteries) is a world-changing concept.